150 lines
5.5 KiB
C
150 lines
5.5 KiB
C
/****************************************************************************
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* sched/sched_addreadytorun.c
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*
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* Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name NuttX nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdbool.h>
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#include <queue.h>
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#include <assert.h>
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#include "os_internal.h"
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/****************************************************************************
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* Private Type Declarations
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****************************************************************************/
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/****************************************************************************
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* Global Variables
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****************************************************************************/
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/****************************************************************************
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* Private Variables
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****************************************************************************/
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/****************************************************************************
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* Private Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: sched_addreadytorun
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*
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* Description:
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* This function adds a TCB to the ready to run
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* list. If the currently active task has preemption disabled
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* and the new TCB would cause this task to be preempted, the
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* new task is added to the g_pendingtasks list instead. The
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* pending tasks will be made ready-to-run when preemption
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* is unlocked.
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*
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* Inputs:
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* btcb - Points to the blocked TCB that is ready-to-run
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*
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* Return Value:
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* true if the currently active task (the head of the
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* g_readytorun list) has changed.
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*
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* Assumptions:
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* - The caller has established a critical section before
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* calling this function (calling sched_lock() first is NOT
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* a good idea -- use irqsave()).
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* - The caller has already removed the input rtcb from
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* whatever list it was in.
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* - The caller handles the condition that occurs if the
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* the head of the g_readytorun list is changed.
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*
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****************************************************************************/
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bool sched_addreadytorun(FAR _TCB *btcb)
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{
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FAR _TCB *rtcb = (FAR _TCB*)g_readytorun.head;
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bool ret;
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/* Check if pre-emption is disabled for the current running
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* task and if the new ready-to-run task would cause the
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* current running task to be preempted.
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*/
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if (rtcb->lockcount && rtcb->sched_priority < btcb->sched_priority)
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{
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/* Yes. Preemption would occur! Add the new ready-to-run
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* task to the g_pendingtasks task list for now.
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*/
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sched_addprioritized(btcb, (FAR dq_queue_t*)&g_pendingtasks);
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btcb->task_state = TSTATE_TASK_PENDING;
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ret = false;
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}
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/* Otherwise, add the new task to the g_readytorun task list */
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else if (sched_addprioritized(btcb, (FAR dq_queue_t*)&g_readytorun))
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{
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/* Information the instrumentation logic that we are switching tasks */
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sched_note_switch(rtcb, btcb);
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/* The new btcb was added at the head of the g_readytorun list. It
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* is now to new active task!
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*/
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ASSERT(!rtcb->lockcount && btcb->flink != NULL);
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btcb->task_state = TSTATE_TASK_RUNNING;
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btcb->flink->task_state = TSTATE_TASK_READYTORUN;
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ret = true;
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}
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else
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{
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/* The new btcb was added in the middle of the g_readytorun list */
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btcb->task_state = TSTATE_TASK_READYTORUN;
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ret = false;
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}
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return ret;
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}
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